Systems and methods for out-of-band interference mitigation

ABSTRACT

A system for interference mitigation including a transmit coupler that samples the RF transmit signal to create a sampled RF transmit signal; a transmit analog canceller that transforms the RF transmit signal to an RF interference cancellation signal, according to a first configuration state; a first receive coupler that combines the RF interference cancellation signal and the RF receive signal to generate a composite RF receive signal; a sampling analog interference filtering system that, in order to remove interference in the transmit band, filters the sampled RF transmit signal to generate a cleaned transmit signal; a first frequency downconverter that converts the transmit signal to a BB transmit signal; a second frequency downconverter that converts the composite RF receive signal to a composite BB receive signal; and an analog-to-digital converter that converts the transmit signal to a digital transmit signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/378,180, filed on 14Dec. 2016, which claims the benefit of U.S.Provisional Application Ser. No. 62/268,400, filed on 16Dec. 2015, allof which are incorporated in their entireties by this reference.

TECHNICAL FIELD

This invention relates generally to the wireless communications field,and more specifically to new and useful systems and methods forout-of-band interference mitigation.

BACKGROUND

Traditional wireless communication systems are half-duplex; that is,they are not capable of transmitting and receiving signalssimultaneously on a single wireless communications channel. One way thatthis issue is addressed is through the use of frequency divisionmultiplexing (FDM), in which transmission and reception occur ondifferent frequency channels. Unfortunately, the performance ofFDM-based communication is limited by the issue of adjacent-channelinterference (ACI), which occurs when a transmission on a firstfrequency channel contains non-negligible strength in another frequencychannel used by a receiver. ACI may be addressed by increasing channelseparation, but this in turn limits the bandwidth available for use in agiven area. ACI may also be addressed by filtering, but the use offilters alone may result in inadequate performance for manyapplications. Thus, there is a need in the wireless communications fieldto create new and useful systems and methods for out-of-bandinterference mitigation. This invention provides such new and usefulsystems and methods.

BRIEF DESCRIPTION OF THE FIG.S

FIG. 1 is a prior art representation of out-of-band interferencemitigation;

FIG. 2 is a diagram representation of a system of a preferredembodiment;

FIG. 3 is a diagram representation of a system of a preferredembodiment;

FIG. 4 is a diagram representation of a system of a preferredembodiment;

FIG. 5 is a diagram representation of a system of a preferredembodiment;

FIG. 6 is a diagram representation of a system of a preferredembodiment;

FIG. 7 is a diagram representation of a system of a preferredembodiment;

FIG. 8 is a diagram representation of a system of a preferredembodiment;

FIG. 9 is a diagram representation of a digital interference cancellerof a system of a preferred embodiment;

FIG. 10 is a diagram representation of an analog interference cancellerof a system of a preferred embodiment;

FIG. 11 is a diagram representation of a system of a preferredembodiment;

FIG. 12 is a diagram representation of a system of a preferredembodiment;

FIG. 13 is a diagram representation of a system of a preferredembodiment;

FIG. 14 is a diagram representation of a system of a preferredembodiment; and

FIG. 15 is a diagram representation of a system of a preferredembodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the inventionis not intended to limit the invention to these preferred embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

1. Out-Of-Band Interference Mitigation Systems

A system woo for out-of-band interference mitigation includes a receiveband interference cancellation system (RxICS) 1300 and at least one of atransmit band interference cancellation system (TxICS) 1100 and atransmit band interference filtering system (TxIFS) 1200. The system woomay additionally or alternatively include a receive band filteringsystem (RxIFS) 1400. The system woo may additionally include any numberof additional elements to enable interference cancellation and/orfiltering, including signal couplers 1010, amplifiers 1020, frequencyupconverters 1030, frequency downconverters 1040, analog-to-digitalconverters (ADC) 1050, digital-to-analog converters (DAC) 1060, timedelays 1070, and any other circuit components (e.g., phase shifters,attenuators, transformers, filters, etc.).

The system woo is preferably implemented using digital and/or analogcircuitry. Digital circuitry is preferably implemented using ageneral-purpose processor, a digital signal processor, an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA) and/or any suitable processor(s) or circuit(s). Analog circuitryis preferably implemented using analog integrated circuits (ICs) but mayadditionally or alternatively be implemented using discrete components(e.g., capacitors, resistors, transistors), wires, transmission lines,waveguides, digital components, mixed-signal components, or any othersuitable components. The system woo preferably includes memory to storeconfiguration data, but may additionally or alternatively be configuredusing externally stored configuration data or in any suitable manner.

The system woo functions to reduce interference present in acommunications receiver resulting from transmission of a nearbytransmitter on an adjacent communications channel (e.g.,adjacent-channel interference). Adjacent-channel interference may resultfrom either or both of a receiver receiving transmissions outside of adesired receive channel and a transmitter transmitting (eitherintentionally or via leakage) on the desired receive channel.

Traditionally, adjacent-channel interference has been mitigated usingtunable or selectable filter-based architectures; for example, as shownin FIG. 1. On the transmit side, the tunable radio frequency (RF) filteris used to suppress the transmit signal in the receive band (e.g., abandpass filter that only lets the transmit band pass). On the receiveside, the tunable RF filter is generally used to suppress interferencedue to the transmitted signal in the transmit band (e.g., a bandpassfilter that only lets the receive band pass). In some cases, this filtermay also be used to selectively filter signal in the receive band aswell.

This purely filter-based approach is limited primarily by its ability toremove interference in the receive band. Filtering in the receive bandprimarily occurs at the transmit side. Since, frequently, out-of-channelsignal results from non-linear processes such as amplification, thisfiltering must generally occur at RF and after power amplification,which means that the transmit filter must both be able to reject a largeamount of signal out-of-band without a large insertion loss. In otherwords, in these cases the filter must generally have a high qualityfactor (Q factor, Q), high insertion loss, or low interference rejectionability.

Likewise, the RF filter on the receive side must also be able to rejecta large amount of signal out-of-band (since the transmit side filterdoes not filter the transmit band signal), and so it must also have highQ, high insertion loss, or low interference rejection ability. Note thatthese limitations are especially apparent in cases where the transmitand receive antennas are nearby (i.e., antenna isolation is low),because the amount of power that must be rejected by the RF filtersincreases; or when channel separation is small (and therefore filter Qmust be higher).

The system woo provides improved interference mitigation by performinginterference cancellation either as a substitute for or in addition tointerference filtering. The system 1000 uses a receive band interferencecancellation system (RxICS 1300) to remove interference in the receiveband, as well as either or both of the transmit band interferencecancellation system (TxICS 1100) and transmit band interferencefiltering system (TxIFS 1200) to remove interference in the transmitband.

The system woo may be arranged in various architectures including theseelements, enabling flexibility for a number of applications. In someembodiments, the system 1000 may be attached or coupled to existingtransceivers; additionally or alternatively, the system 1000 may beintegrated into transceivers. Examples of architectures of the system1000 are as shown in FIGS. 2-7.

As shown in FIG. 2, the system woo may mitigate interference using theTxICS 1100 and RxICS 1300 (as well as optionally the RxIFS 1400),combining the RxICS 1300 interference cancellation with a basebandreceive signal.

As shown in FIG. 3, the system woo may mitigate interference using theTxICS 1100 and RxICS 1300 (as well as optionally the RxIFS 1400),combining the RxICS 1300 interference cancellation with an RF receivesignal.

As shown in FIG. 4, the system woo may mitigate interference using theTxIFS 1200 and RxICS 1300 (as well as optionally the RxIFS 1400),combining the RxICS 1300 interference cancellation with a basebandreceive signal.

As shown in FIG. 5, the system woo may mitigate interference using theTxIFS 1200 and RxICS 1300 (as well as optionally the RxIFS 1400),combining the RxICS 1300 interference cancellation with an RF receivesignal.

As shown in FIG. 6, the system woo may mitigate interference using theTxICS 1100 and RxICS 1300, combining the RxICS 1300 interferencecancellation with a digital receive signal.

As shown in FIG. 7, the system woo may mitigate interference using theTxIFS 1200 and RxICS 1300, combining the RxICS 1300 interferencecancellation with a digital receive signal.

As shown in FIG. 8, the system woo may mitigate interference using theTxIFS 1200 and RxICS 1300, combining the RxICS 1300 interferencecancellation with an analog receive signal.

In one implementation of a preferred embodiment, the RxICS 1300 caninclude a switchable output, enabling combination of the RxICS 1300interference cancellation with a digital receive signal, an analogreceive signal, and/or an RF receive signal. The RxICS 1300 may includean RxDC 1310 with an output switchable between a digital ouput, abaseband analog output (after digital-to-analog conversion), and anIF/RF analog output (after frequency upconversion of the analog output).Additionally or alternatively, the RxICS 1300 may include an RxAC 1320with an output switchable between an RF output, a baseband/IF analogoutput (after frequency downconversion of the RF output), and a digitaloutput (after analog-to-digital conversion of the analog output).Selection of which interference cancellation output to combine with theappropriate receive signal is preferably performed by a tuning circuit,but can additionally or alternatively be performed by any suitablecontroller. In this implementation, the tuning circuit preferablyreceives feedback signals from the receive path at the RF, baseband, anddigital signal paths, and the output is selected (e.g., by the tuningcircuit) according to changes in the feedback signal that are indicativeof optimal interference-cancellation performance. Similarly, the TxICS1100 can include a switchable output as described above, but directed toperforming interference cancellation in the transmit band in lieu of thereceive band.

The system 1000 is preferably coupled to or integrated with a receiverthat functions to receive analog receive signals transmitted over acommunications link (e.g., a wireless channel, a coaxial cable). Thereceiver preferably converts analog receive signals into digital receivesignals for processing by a communications system, but may additionallyor alternatively not convert analog receive signals (passing themthrough directly without conversion).

The receiver is preferably coupled to the communications link by aduplexer-coupled RF antenna, but may additionally or alternatively becoupled to the communications link in any suitable manner. Some examplesof alternative couplings include coupling via one or more dedicatedreceive antennas. In another alternative coupling, the receiver may becoupled to the communications link by a circulator-coupled RF antenna.

The receiver preferably includes an ADC 1050 (described in followingsections) and converts baseband analog signals to digital signals. Thereceiver may additionally or alternatively include an integratedamplifier 1020 and/or a frequency downconverter 1040 (enabling thereceiver to convert RF or other analog signals to digital).

The system 1000 is preferably coupled to or integrated with atransmitter that functions to transmit signals of the communicationssystem over a communications link to a second communications system. Thetransmitter preferably converts digital transmit signals into analogtransmit signals.

The transmitter is preferably coupled to the communications link by aduplexer-coupled RF antenna, but may additionally or alternatively becoupled to the communications link in any suitable manner. Some examplesof alternative couplings include coupling via one or more dedicatedtransmit antennas, dual-purpose transmit and/or receive antennas, or anyother suitable antennas. In other alternative couplings, the transmittermay be coupled to the communications link by direct wired coupling(e.g., through one or more RF coaxial cables, transmission linecouplers, etc.).

The transmitter preferably includes a DAC 1060 (described in followingsections) and converts digital signals to baseband analog signals. Thetransmitter may additionally or alternatively include an integratedamplifier 1020 and/or a frequency upconverter 1030 (enabling thetransmitter to convert digital signals to RF signals and/or intermediatefrequency (IF) signals).

The transmitter and receiver may be coupled to the same communicatingdevice or different communicating devices. In some variations, there maybe multiple transmitters and/or receivers, which may be coupled to thesame or different communication devices in any suitable combination.

Signal couplers 1010 function to allow analog signals to be split and/orcombined. While not necessarily shown in the figures, signal couplersare preferably used at each junction (e.g., splitting, combining) of twoor more analog signals; alternatively, analog signals may be coupled,joined, or split in any manner. In particular, signal couplers 1010 maybe used to provide samples of transmit signals, as well as to combineinterference cancellation signals with other signals (e.g., transmit orreceive signals). Alternatively, signal couplers 1010 may be used forany purpose. Signal couplers 1010 may couple and/or split signals usingvarying amounts of power; for example, a signal coupler 1010 intended tosample a signal may have an input port, an output port, and a sampleport, and the coupler 1010 may route the majority of power from theinput port to the output port with a small amount going to the sampleport (e.g., a 99.9%/0.1% power split between the output and sample port,or any other suitable split).

The signal coupler 1010 is preferably a short section directionaltransmission line coupler, but may additionally or alternatively be anypower divider, power combiner, directional coupler, or other type ofsignal splitter. The signal coupler 130 is preferably a passive coupler,but may additionally or alternatively be an active coupler (forinstance, including power amplifiers). For example, the signal coupler1010 may comprise a coupled transmission line coupler, a branch-linecoupler, a Lange coupler, a Wilkinson power divider, a hybrid coupler, ahybrid ring coupler, a multiple output divider, a waveguide directionalcoupler, a waveguide power coupler, a hybrid transformer coupler, across-connected transformer coupler, a resistive tee, and/or a resistivebridge hybrid coupler. The output ports of the signal coupler 1010 arepreferably phase-shifted by ninety degrees, but may additionally oralternatively be in phase or phase shifted by a different amount.

Amplifiers 1020 function to amplify signals of the system 1000.Amplifiers may include any analog or digital amplifiers. Some examplesof amplifiers 1020 include low-noise amplifiers (LNA) typically used toamplify receive signals and power amplifiers (PA) typically used toamplify transmit signals prior to transmission.

Frequency upconverters 1030 function to upconvert a carrier frequency ofan analog signal (typically from baseband to RF, but alternatively fromany frequency to any other higher frequency). Upconverters 1030preferably accomplish signal upconversion using heterodyning methods,but may additionally or alternatively use any suitable upconversionmethods.

The upconverter 1030 preferably includes a local oscillator (LO), amixer, and a bandpass filter. The local oscillator functions to providea frequency shift signal to the mixer; the mixer combines the frequencyshift signal and the input signal to create (usually two, butalternatively any number) frequency shifted signals, one of which is thedesired output signal, and the bandpass filter rejects signals otherthan the desired output signal.

The local oscillator is preferably a digital crystal variable-frequencyoscillator (VFO) but may additionally or alternatively be an analog VFOor any other suitable type of oscillator. The local oscillatorpreferably has a tunable oscillation frequency but may additionally oralternatively have a static oscillation frequency.

The mixer is preferably an active mixer, but may additionally oralternatively be a passive mixer. The mixer may comprise discretecomponents, analog integrated circuits (ICs), digital ICs, and/or anyother suitable components. The mixer preferably functions to combine twoor more electrical input signals into one or more composite outputs,where each output includes some characteristics of at least two inputsignals.

The bandpass filter is preferably a tunable bandpass filter centeredaround an adjustable radio frequency. Additionally or alternatively, thebandpass filter may be a bandpass filter centered around a set radiofrequency, or any other suitable type of filter. The bandpass filter ispreferably a passive filter, but may additionally or alternatively be anactive filter. The bandpass filter is preferably implemented with analogcircuit components, but may additionally or alternatively be digitallyimplemented.

In variations in which the bandpass filter is tunable, the centerfrequency of each tunable filter is preferably controlled by a controlcircuit or tuning circuit, but may additionally or alternatively becontrolled by any suitable system (including manually controlled, e.g.as in a mechanically tuned capacitor). Each tunable bandpass filterpreferably has a set quality (Q) factor, but may additionally oralternatively have a variable Q factor. The tunable bandpass filters mayhave different Q factors; for example, some of the tunable filters maybe high-Q, some may be low-Q, and some may be no-Q (flat response).

Frequency downconverters 1040 function to downconvert the carrierfrequency of an analog signal (typically to baseband, but alternativelyto any frequency lower than the carrier frequency). The downconverter1040 preferably accomplishes signal downconversion using heterodyningmethods, but may additionally or alternatively use any suitabledownconversion methods.

The downconverter 1040 preferably includes a local oscillator (LO), amixer, and a baseband filter. The local oscillator functions to providea frequency shift signal to the mixer; the mixer combines the frequencyshift signal and the input signal to create (usually two) frequencyshifted signals, one of which is the desired signal, and the basebandfilter rejects signals other than the desired signal.

The local oscillator is preferably a digital crystal variable-frequencyoscillator (VFO) but may additionally or alternatively be an analog VFOor any other suitable type of oscillator. The local oscillatorpreferably has a tunable oscillation frequency but may additionally oralternatively have a static oscillation frequency.

The mixer is preferably an active mixer, but may additionally oralternatively be a passive mixer. The mixer may comprise discretecomponents, analog ICs, digital ICs, and/or any other suitablecomponents. The mixer preferably functions to combine two or moreelectrical input signals into one or more composite outputs, where eachoutput includes some characteristics of at least two input signals.

The baseband filter is preferably a lowpass filter with a tunablelow-pass frequency. Additionally or alternatively, the baseband filtermay be a lowpass filter with a set low-pass frequency, a bandpassfilter, or any other suitable type of filter. The baseband filter ispreferably a passive filter, but may additionally or alternatively be anactive filter. The baseband filter is preferably implemented with analogcircuit components, but may additionally or alternatively be digitallyimplemented.

While the bandpass filter of the frequency upconverter 1030 and thebaseband filter of the frequency downconverter 1040 are necessary forperforming frequency upconversion and downconversion, they also may beuseful for filtering transmit and/or receive band signals. This isdiscussed in more detail in the sections on filtering and cancellationsystems 1100, 1200, 1300, and 1400, but in general, the same filtersthat reject image frequencies generated by mixers may also rejectsignals outside of a desired band of interest.

For example, an RF receive signal may contain one or more signalcomponents in a receive band (at 5690 MHz) and interference due to anundesired signal in a nearby transmit band (at 5670 MHz). When thesesignals are downconverted to baseband by a receiver (or otherdownconverter with an LO at the receive band frequency), they are firstprocessed by the mixer, which generates four signals:

5690 MHz±5690 MHz and 5690 MHz±5670 MHz

0 MHz, 20 MHz, 11.38 GHz, 11.36 GHz

The 11 GHz frequencies are easily filtered by the filter of thedownconverter, but the filter may additionally be used to filter outthat 20 MHz signal as well (reducing transmit band presence in thebaseband receive signal). In this way, frequency downconversion can beused to assist other filtering or interference cancellation systems ofthe system 1000.

Note that while the upconverter 1040 also performs filtering, and thatfiltering may be used to filter out undesired signals, filtering duringupconversion may be less effective than filtering during downconversion.One reason for this is architecture-based; power amplification istypically performed after upconversion (and power amplification mayamount for a large part of interference generation in other bands). Thatbeing said, it may still be useful to filter a signal prior toamplification, and noisy amplification is not always performed for allupconverted signals (e.g., digital transmit signal samples converted toRF). Another reason is that the upconverter bandpass frequency iscentered around the RF frequency (or other frequency higher thanbaseband), which means that for a given amount of cancellation required,the filter must have a higher quality factor (Q).

For example, if a filter is desired to reject 30 dB at 20 MHz away froman RF center frequency of 5 GHz (that is, after upconversion or beforedownconversion), the Q of that filter must be higher than a low-passfilter desired to rejected 30 dB at 20 MHz away from baseband.

Analog-to-digital converters (ADCs) 1050 function to convert analogsignals (typically at baseband, but additionally or alternatively at anyfrequency) to digital signals. ADCs 1050 may be any suitableanalog-to-digital converter; e.g., a direct-conversion ADC, a flash ADC,a successive-approximation ADC, a ramp-compare ADC, a Wilkinson ADC, anintegrating ADC, a delta-encoded ADC, a time-interleaved ADC, or anyother suitable type of ADC.

Digital-to-analog converters (DACs) 1060 function to convert digitalsignals to analog signals (typically at baseband, but additionally oralternatively at any frequency). The DAC 1060 may be any suitabledigital-to-analog converter; e.g., a pulse-width modulator, anoversampling DAC, a binary-weighted DAC, an R-2R ladder DAC, a cyclicDAC, a thermometer-coded DAC, or a hybrid DAC.

Time delays 1070 function to delay signal components. Delays 1070 may beimplemented in analog (e.g., as a time delay circuit) or in digital(e.g., as a time delay function). Delays 1070 may be fixed, but mayadditionally or alternatively introduce variable delays. The delay 1070is preferably implemented as an analog delay circuit (e.g., abucket-brigade device, a long transmission line, a series of RCnetworks) but may additionally or alternatively be implemented in anyother suitable manner. If the delay 1070 is a variable delay, the delayintroduced may be set by a tuning circuit or other controller of thesystem 1000. Although not necessarily explicitly shown in figures,delays 1070 may be coupled to the system 1000 in a variety of ways todelay one signal relative to another. For example, delays 1070 may beused to delay a receive or transmit signal to account for time taken togenerate an interference cancellation signal (so that the two signalsmay be combined with the same relative timing). Delays 1070 maypotentially be implemented as part of or between any two components ofthe system 1000.

The TxICS 1100 functions to mitigate interference present in thetransmit band of a signal using self-interference cancellationtechniques; that is, generating a self-interference cancellation signalby transforming signal samples of a first signal (typically a transmitsignal) into a representation of self-interference present in anothersignal (e.g., a receive signal, a transmit signal after amplification,etc.), due to transmission of the first signal and then subtracting thatinterference cancellation signal from the other signal.

The TxICS 1100 is preferably used to cancel interference present in thetransmit band of a receive signal; i.e., the TxICS 1100 generates aninterference cancellation signal from samples of a transmit signal usinga circuit that models the representation of the transmit signal, in thetransmit band, as received by a receiver, and subtracts thatcancellation signal from the receive signal.

The TxICS 1100 may additionally be used to cancel interference presentin the transmit band (TxB) of a transmit signal sample; i.e., the TxICS1100 generates an interference cancellation signal from samples of atransmit signal using a circuit that models the representation of thetransmit signal, in the transmit band, as generated by a transmitter(generally, but not necessarily, before transmission at an antenna), andsubtracts that cancellation signal from the transmit signal sample. Thistype of interference cancellation is generally used to ‘clean’ atransmit signal sample; that is, to remove transmit band signal of atransmit sample, so that the sample contains primarily information inthe receive band (allowing the sample to be used to perform receive-bandinterference cancellation, typically using the RxICS 1300).

The TxICS 1100 comprises at least one of a digital TX interferencecanceller (TxDC) 1110 and an analog TX interference canceller (TxAC)1120. In the case that the TxICS 1100 performs both receive signalcancellation and transmit sample cancellation, the TxICS 1100 mayinclude separate cancellers to perform these tasks; additionally oralternatively, the TxICS 1100 may include any number of cancellers forany purpose (e.g., one canceller performs both tasks, many cancellersperform a single task, etc.).

The TxDC 1110 functions to produce a digital interference cancellationsignal from a digital input signal according to a digital transformconfiguration. The TxDC 1110 may be used to cancel interference in anysignal, using any input, but the TxDC 1110 is preferably used to canceltransmit band interference in an analog receive signal (by converting adigital interference cancellation signal to analog using a DAC 1060 andcombining it with the analog receive signal). The TxDC 1110 may also beused to cancel transmit band signal components in a transmit signal (toperform transmit signal cleaning as previously described).

Using upconverters 1030, downconverters 1040, ADCs 1050, and DACs 1060,the TxDC 1110 may convert analog signals of any frequency to digitalinput signals, and may additionally convert interference cancellationsignals from digital to analog signals of any frequency.

The digital transform configuration of the TxDC 1110 includes settingsthat dictate how the TxDC 1110 transforms a digital transmit signal to adigital interference signal (e.g. coefficients of a generalized memorypolynomial used to transform a transmit signal to an interferencecancellation signal). The transform configuration for a TxDC 1110 ispreferably set adaptively by a transform adaptor, but may additionallyor alternatively be set by any component of the system woo (e.g., atuning circuit) or fixed in a set transform configuration.

The TxDC 1110 is preferably substantially similar to the digitalself-interference canceller of U.S. Provisional Application No.62/268,388, the entirety of which is incorporated by this reference,except in that the TxDC 1110 is not necessarily applied solely tocancellation of interference in a receive signal resulting fromtransmission of another signal (as previously described).

In one implementation of a preferred embodiment, the TxDC 1110 includesa component generation system, a multi-rate filter, and a transformadaptor, as shown in FIG. 9.

The component generation system functions to generate a set of signalcomponents from the sampled input signal (or signals) that may be usedby the multi-rate filter to generate an interference cancellationsignal. The component generation system preferably generates a set ofsignal components intended to be used with a specific mathematical model(e.g., generalized memory polynomial (GMP) models, Volterra models, andWiener-Hammerstein models); additionally or alternatively, the componentgeneration system may generate a set of signal components usable withmultiple mathematical models.

In some cases, the component generator may simply pass a copy of asampled transmit signal unmodified; this may be considered functionallyequivalent to a component generator not being explicitly included forthat particular path.

The multi-rate adaptive filter functions to generate an interferencecancellation signal from the signal components produced by the componentgeneration system. In some implementations, the multi-rate adaptivefilter may additionally function to perform sampling rate conversions(similarly to an upconverter 1030 or downconverter 1040, but applied todigital signals). The multi-rate adaptive filter preferably generates aninterference cancellation signal by combining a weighted sum of signalcomponents according to mathematical models adapted to modelinterference contributions of the transmitter, receiver, channel and/orother sources. Examples of mathematical models that may be used by themulti-rate adaptive filter include generalized memory polynomial (GMP)models, Volterra models, and Wiener-Hammerstein models; the multi-rateadaptive filter may additionally or alternatively use any combination orset of models.

The transform adaptor functions to set the transform configuration ofthe multi-rate adaptive filter and/or the component generation system.The transform configuration preferably includes the type of model ormodels used by the multi-rate adaptive filter as well as configurationdetails pertaining to the models (each individual model is a model typepaired with a particular set of configuration details). For example, onetransform configuration might set the multi-rate adaptive filter to usea GMP model with a particular set of coefficients. If the model type isstatic, the transform configuration may simply include modelconfiguration details; for example, if the model is always a GMP model,the transform configuration may include only coefficients for the model,and not data designating the model type.

The transform configuration may additionally or alternatively includeother configuration details related to the signal component generationsystem and/or the multi-rate adaptive filter. For example, if the signalcomponent generation system includes multiple transform paths, thetransform adaptor may set the number of these transform paths, whichmodel order their respective component generators correspond to, thetype of filtering used, and/or any other suitable details. In general,the transform configuration may include any details relating to thecomputation or structure of the signal component generation systemand/or the multi-rate adaptive filter.

The transform adaptor preferably sets the transform configuration basedon a feedback signal sampled from a signalpost-interference-cancellation (i.e., a residue signal). For example,the transform adaptor may set the transform configuration iteratively toreduce interference present in a residue signal. The transform adaptormay adapt transform configurations and/ortransform-configuration-generating algorithms using analytical methods,online gradient-descent methods (e.g., LMS, RLMS), and/or any othersuitable methods. Adapting transform configurations preferably includeschanging transform configurations based on learning. In the case of aneural-network model, this might include altering the structure and/orweights of a neural network based on test inputs. In the case of a GMPpolynomial model, this might include optimizing GMP polynomialcoefficients according to a gradient-descent method.

Note that TxDC 1110 may share transform adaptors and/or other components(although each TxDC 1110 is preferably associated with its own transformconfiguration).

The TxAC 1120 functions to produce an analog interference cancellationsignal from an analog input signal. The TxAC 1120 may be used to cancelinterference in any signal, using any input, but the TxAC 1120 ispreferably used to cancel transmit band interference in an analogreceive signal. The TxAC 1120 may also be used to cancel transmit bandsignal components in a transmit signal sample (to perform transmitsignal cleaning as previously described).

Using upconverters 1030, downconverters 1040, ADCs 1050, and DACs 1060,the TXAC 1120 may convert digital signals to analog input signals, andmay additionally convert interference cancellation signals from analogto digital (or to another analog signal of different frequency).

The TXAC 1120 is preferably designed to operate at a single frequencyband, but may additionally or alternatively be designed to operate atmultiple frequency bands. The TXAC 1120 is preferably substantiallysimilar to the circuits related to analog self-interference cancellationof U.S. patent application Ser. No. 14/569,354 (the entirety of which isincorporated by this reference); e.g., the RF self-interferencecanceller, the IF self-interference canceller, associatedup/downconverters, and/or tuning circuits, except that the TXAC 1120 isnot necessarily applied solely to cancellation of interference in areceive signal resulting from transmission of another signal (aspreviously described).

The TXAC 1120 is preferably implemented as an analog circuit thattransforms an analog input signal into an analog interferencecancellation signal by combining a set of filtered, scaled, and/ordelayed versions of the analog input signal, but may additionally oralternatively be implemented as any suitable circuit. For instance, theTXAC 1120 may perform a transformation involving only a single version,copy, or sampled form of the analog input signal. The transformed signal(the analog interference cancellation signal) preferably represents atleast a part of an interference component in another signal.

The TXAC 1120 is preferably adaptable to changing self-interferenceparameters in addition to changes in the input signal; for example,transceiver temperature, ambient temperature, antenna configuration,humidity, and transmitter power. Adaptation of the TXAC 1120 ispreferably performed by a tuning circuit, but may additionally oralternatively be performed by a control circuit or other controlmechanism included in the canceller or any other suitable controller(e.g., by the transform adaptor of the TxDC 1110).

In one implementation of a preferred embodiment, the TXAC 1120 includesa set of scalers (which may perform gain, attenuation, or phaseadjustment), a set of delays, a signal combiner, a signal divider, and atuning circuit, as shown in FIG. 10. In this implementation the TXAC1120 may optionally include tunable filters (e.g., bandpass filtersincluding an adjustable center frequency, lowpass filters including anadjustable cutoff frequency, etc.).

The tuning circuit preferably adapts the TXAC 1120 configuration (e.g.,parameters of the filters, scalers, delayers, signal divider, and/orsignal combiner, etc.) based on a feedback signal sampled from a signalafter interference cancellation is performed (i.e., a residue signal).For example, the tuning circuit may set the TXAC 1120 configurationiteratively to reduce interference present in a residue signal. Thetuning circuit preferably adapts configuration parameters using onlinegradient-descent methods (e.g., LMS, RLMS), but configuration parametersmay additionally or alternatively be adapted using any suitablealgorithm. Adapting configuration parameters may additionally oralternatively include alternating between a set of configurations. Notethat TxACs may share tuning circuits and/or other components (althougheach TxAC 1120 is preferably associated with a unique configuration orarchitecture). The tuning circuit may be implemented digitally and/or asan analog circuit.

In one implementation of a preferred embodiment, the TxICS 1100 performsinterference cancellation solely using analog cancellation, as shown inFIG. 11. In this implementation, the TxICS 1100 includes a TxAC 1120(RxCan) used to cancel transmit band signal components present in thereceive signal as well as a TXAC 1120 used to clean transmit signalsamples (as previously described) for use by an RxICS 1300; bothcancellers are controlled by a single tuning circuit, which receivesinput from both the transmit signal and from the residue signal. Notethat as shown in FIG. 11, the tuning circuit takes a baseband feedbacksignal from the downconverter 1040 after mixing, but prior to finalfiltering. While it would also be possible for the tuning circuit toreceive an RF feedback signal from before the downconverter 1040, notethat in this implementation the filter of the downconverter 1040 may beused to remove transmit band signal components remaining aftercancellation. Because the presence of these signal components prior tofiltering is an indication of the performance of the RxCan TxAC 1120, itmay be preferred for the tuning circuit to sample a residue signal priorto filtering that removes transmit band signal components.Alternatively, the tuning circuit may sample any signals at any point.

In a variation of this implementation, the system may utilize acombination of transmit band filtering (using TxIFS 1200) andcancellation, as shown in FIG. 12.

As shown in FIGS. 11 and 12, the RxICS 1300 (including an RxDC 1310 andassociated components) is implemented digitally, but may additionally oralternatively be implemented in analog (including an RxAC 1320 andassociated components), as shown in FIGS. 13 and 14. The TxICS 1100and/or RxICS 1300 may be implemented in digital domains, analog domains,or a combination of the two.

In one implementation of a preferred embodiment, the TxICS 1100 performsinterference cancellation solely using digital cancellation, as shown inFIG. 15. In this implementation, the TxICS 1100 includes a TxDC 1110(RxCan) used to cancel transmit band signal components present in thereceive signal as well as a TxDC 1110 (Sample) used to clean transmitsignal samples for use by an RxICS 1300; both cancellers are controlledby a single transform adaptor, which receives input from both thetransmit signal and from the residue signal. Note that in thisimplementation, the RxDC 1310 receives an input signal derived from acombination of the upconverted output of the Sample TxDC 1110 with theupconverted transmit signal, but additionally or alternatively the RxDC1310 may receive an input signal directly from the digital transmitpath. As shown in FIGS. 11 and 12, the RxICS 1300 is implementeddigitally, but may additionally or alternatively be implemented inanalog, as shown in FIGS. 13 and 14. The TxICS 1100 and/or RxICS 1300may be implemented in digital domains, analog domains, or a combinationof the two.

Note that while as shown in these FIGS. the TxCan and Sample cancellerssample the transmit signal on parallel paths, multiple cancellers of theTxICS 1100 may share switched signal paths (e.g., the coupler 1010coupled to the transmit antenna in FIG. 11 may switch between the RxCanTxAC 1120 and the Sampling TXAC 1120).

The TxIFS 1200 functions to mitigate interference present in thetransmit band of a signal by performing filtering in the transmit band.The TxIFS 1200 is preferably used to filter out interference present inthe transmit band of a receive signal; e.g., the TxIFS 1200 includes afilter on the receive signal that allows signal components in thereceive band to pass while blocking signal components in the transmitband.

The TxIFS 1200 may additionally or alternatively be used to filter outinterference present in the transmit band of a transmit signal sample;e.g., to generate a transmit signal sample that includes primarilysignal components in the receive band (as a way to estimate interferencegenerated in the receive band of the receive signal by the transmitsignal). Transmit samples cleaned in this way may be used to performreceive-band interference cancellation, typically using the RxICS 1300.

The TxIFS 1200 preferably includes one or more tunable bandpass filters.Alternatively, the TxIFS 1200 may include any type of filter. Forexample, the TxIFS 1200 may include a notch filter to remove transmitband signal components only. Filters of the TxIFS 1200 are preferablyused for RF signals, but may additionally or alternatively be used forany frequency analog signal.

Filters of the TxIFS 1200 preferably transform signal componentsaccording to the response of the filter, which may introduce a change insignal magnitude, signal phase, and/or signal delay. Filters of theTxIFS 1200 are preferably formed from a combination (e.g., in seriesand/or in parallel) of resonant elements. Resonant elements of thefilters are preferably formed by lumped elements, but may additionallyor alternatively be distributed element resonators, ceramic resonators,SAW resonators, crystal resonators, cavity resonators, or any suitableresonators.

Filters of the TxIFS 1200 are preferably tunable such that one or morepeaks of the filters may be shifted. In one implementation of apreferred embodiment, one or more resonant elements of a filter mayinclude a variable shunt capacitance (e.g., a varactor or a digitallytunable capacitor) that enables filter peaks to be shifted. Additionallyor alternatively, filters may be tunable by quality factor (i.e., Q maybe modified by altering circuit control values), or filters may be nottunable. Filters 145 may include, in addition to resonant elements,delayers, phase shifters, and/or scaling elements. The filters arepreferably passive filters, but may additionally or alternatively beactive filters. The filters are preferably implemented with analogcircuit components, but may additionally or alternatively be digitallyimplemented. The center frequency of any tunable peak of a filter ispreferably controlled by a tuning circuit, but may additionally oralternatively be controlled by any suitable system (including manuallycontrolled, e.g. as in a mechanically tuned capacitor).

In some implementations, the system can include both a TxIFS 1200 and aTxICS 1100 that are cooperatively operated. For example, the TxIFS 1200may include a filter with a tunable quality factor, and TxICS 1100operation may be tuned based on the quality factor of the filter (e.g.,selection of a lower quality factor may cause the TxICS 1100 to beadaptively configured to reduce interference over a wider range ofsignal components). In another example, the TxIFS 1200 and TxICS 1100may be each be switched in and out of the receive and transmit path,respectively (e.g., the TxIFS is switched into the receive path when theTxICS is switched out of the transmit path, and vice versa). The TxIFS1200 and/or TxICS 1100 may additionally or alternatively be configuredin any suitable manner.

The RxICS 1300 functions to mitigate interference present in the receiveband of a signal using self-interference cancellation techniques; thatis, generating a self-interference cancellation signal by transformingsignal samples of a first signal (typically a transmit signal) into arepresentation of self-interference present in another signal, due totransmission of the first signal (e.g., a receive signal, a transmitsignal after amplification, etc.) and then subtracting that interferencecancellation signal from the other signal.

The RxICS 1300 is preferably used to cancel interference present in thereceive band of a receive signal; i.e., the RxICs 1300 generates aninterference cancellation signal from samples of receive band componentsof a transmit signal using a circuit that models the representation ofthe transmit signal, in the receive band, as received by a receiver, andsubtracts that cancellation signal from the receive signal.

The RxICS 1300 preferably receives as input samples of a transmit signalthat has been filtered (e.g., by the TxIFS 1200) or interferencecancelled (e.g., by the TxICS 1100) to reduce the presence of transmitband components (allowing for better estimation of interference due tosignal components of the transmit signal that are in the receive band).

The RxICS 1300 preferably cancels interference on a receive signal thathas already experienced transmit band cancellation and/or filtering, butadditionally or alternatively, the RxICS 1300 may cancel interference ona receive signal that has not experienced transmit band cancellation orfiltering.

The RxICS 1300 comprises at least one of a digital RX interferencecanceller (RxDC) 1310 and an analog RX interference canceller (RxAC)1320.

The RxDC 1310 is preferably substantially similar to the TxDC 1110, butmay additionally or alternatively be any suitable digital interferencecanceller.

The RxAC 1320 is preferably substantially similar to the TxAC 1120, butmay additionally or alternatively be any suitable analog interferencecanceller.

The RxIFS 1400 functions to mitigate interference present in the receiveband of a transmit signal by performing filtering in the receive band.The RxIFS 1400, if present, functions to remove receive-band signalcomponents in a transmit signal prior to transmission (but preferablypost-power-amplification). Filters of the RxIFS 1400 are preferablysubstantially similar to those of the TxIFS 1200, but the RxIFS mayadditionally or alternatively include any suitable filters.

In some implementations, the system can include both an RxIFS 1400 andan RxICS 1300 that are cooperatively operated. For example, the RxIFS1400 may include a filter with a tunable quality factor, and RxICS 1300operation may be tuned based on the quality factor of the filter (e.g.,selection of a lower quality factor may cause the RxICS 1300 to beadaptively configured to reduce interference over a wider range ofsignal components). In another example, the RxIFS 1400 and RxICS 1300may be each be switched in and out of the transmit and receive path,respectively (e.g., the RxIFS is switched into the transmit path whenthe RxICS is switched out of the receive path, and vice versa). TheRxIFS 1400 and/or RxICS 1300 may additionally or alternatively beconfigured in any suitable manner.

In some implementations, the system can include a TxICS 1100, TxIFS1200, RxICS 1300, and RxIFS 1400. Each of the TxICS, TxIFS, RxICS, andRxIFS may be controlled based on the performance and/or operation of anyof the other subsystems, or alternatively based on any suitableconditions. For example, the TxIFS 1200 may include a filter with anadjustable Q-factor, and the RxICS 1300 may include a transform adaptorthat is controlled according to the Q-factor of the filter of the TxIFS1200 (e.g., adjusting the filter to a high Q-factor corresponds to atransform configuration that removes signal components in a narrowfrequency band corresponding to the pass band of the filter).

The methods of the preferred embodiment and variations thereof can beembodied and/or implemented at least in part as a machine configured toreceive a computer-readable medium storing computer-readableinstructions. The instructions are preferably executed bycomputer-executable components preferably integrated with a system forwireless communication. The computer-readable medium can be stored onany suitable computer-readable media such as RAMs, ROMs, flash memory,EEPROMs, optical devices (CD or DVD), hard drives, floppy drives, or anysuitable device. The computer-executable component is preferably ageneral or application specific processor, but any suitable dedicatedhardware or hardware/firmware combination device can alternatively oradditionally execute the instructions.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

We claim:
 1. A system for out-of-band interference mitigationcomprising: a transmit coupler, communicatively coupled to aradio-frequency (RF) transmit signal of a communication system, thatsamples the RF transmit signal to create a sampled RF transmit signal;wherein the RF transmit signal has a first RF carrier frequency in atransmit band; a transmit analog canceller that transforms, according toa first configuration state, the sampled RF transmit signal to a firstRF interference cancellation signal; a first receive coupler,communicatively coupled to an RF receive signal of the communicationsystem having a second RF carrier frequency in a receive band, thatcombines, in order to remove a first portion of interference in thetransmit band, the first RF interference cancellation signal and the RFreceive signal to generate a composite RF receive signal; a samplinganalog interference filtering system that, in order to removeinterference in the transmit band, filters the sampled RF transmitsignal to generate a cleaned transmit signal; a first frequencydownconverter that converts the cleaned transmit signal to a baseband(BB) transmit signal having a BB frequency, wherein the BB frequency isless than the first RF carrier frequency; a second frequencydownconverter that converts the composite RF receive signal to acomposite BB receive signal; an analog-to-digital converter thatconverts the BB transmit signal to a digital transmit signal; a digitalcanceller that transforms the digital transmit signal to a digitalinterference cancellation signal; a digital-to-analog converter thatconverts the digital interference cancellation signal to adigitally-sourced interference cancellation signal; and a second receivecoupler that combines, in order to remove a second portion ofinterference in the receive band, the digitally-sourced interferencecancellation signal and the composite BB receive signal.
 2. The systemof claim 1, further comprising a tuning circuit, wherein the tuningcircuit receives the composite BB receive signal from the receive path,and wherein the tuning circuit sets the first configuration state andthe second configuration state based on changes in the composite BBreceive signal.
 3. The system of claim 1, wherein the transmit band andthe receive band are non-overlapping.
 4. The system of claim 1, whereinthe digital canceller comprises: an adaptive filter that transforms thedigital composite transmit signal into the digital cancellation signalaccording to a transform configuration; a receive analog-to-digitalconverter that converts the baseband composite receive signal to adigital feedback signal; and a transform adaptor that dynamically setsthe transform configuration in response to changes in the digitalfeedback signal.
 5. The system of claim 1, wherein the transmit analogcanceller comprises a signal divider, a set of scalers and delayers, anda signal combiner.
 6. The system of claim 1, wherein the sampling analoginterference filtering system comprises a tunable bandpass filter. 7.The system of claim 6, wherein the tunable bandpass filter is tunable inboth peak frequency response and quality factor.
 8. A system forout-of-band interference mitigation comprising: a transmit coupler,communicatively coupled to a transmit signal of a communication system,that samples the transmit signal to create a sampled transmit signal;wherein the transmit signal has a first center frequency in a transmitband and a signal power in the transmit band; a first canceller thattransforms the sampled transmit signal to a first interferencecancellation signal; a first receive coupler, communicatively coupled toa receive signal of the communication system having a second centerfrequency in a receive band, that combines, in order to remove a firstportion of interference in the transmit band, the first interferencecancellation signal and the receive signal to produce a first compositereceive signal; a sampling interference filtering system that, in orderto remove interference in the transmit band, filters the sampledtransmit signal to generate a cleaned transmit signal; wherein thecleaned transmit signal has a reduced signal power in the transmit band;a second canceller that generates a second interference cancellationsignal based on the cleaned transmit signal; and a second receivecoupler, communicatively coupled to the receive path, that combines, inorder to remove a second portion of interference in the receive band,the second interference cancellation signal and the first compositereceive signal.
 9. The system of claim 8, further comprising a tuningcircuit; wherein the first canceller transforms the sampled transmitsignal to the first interference cancellation signal according to aconfiguration state; wherein the tuning circuit dynamically sets theconfiguration state in response to changes in the first compositereceive signal.
 10. The system of claim 8, wherein the transmit band andthe receive band are non-overlapping.
 11. The system of claim 10,further comprising a receive-band filter, communicatively coupled to thetransmit path between the transmit coupler and a transmit antenna, thatfilters the transmit signal to remove signal components of the transmitsignal within the receive band.
 12. The system of claim 8, wherein thetransmit signal is a digital transmit signal, wherein the firstcanceller is a first digital canceller, wherein the first interferencecancellation signal is a first digital interference cancellation signal,wherein the second canceller is a second digital canceller, and whereinthe second interference cancellation signal is a second digitalinterference cancellation signal.
 13. The system of claim 12, whereinthe first digital canceller comprises: a signal component generationsystem, coupled to the digital transmit signal, that generates a set ofsignal components from the digital transmit signal; a multi-rateadaptive filter that transforms the set of signal components into thefirst digital interference cancellation signal according to a transformconfiguration; and a transform adaptor that dynamically sets thetransform configuration in response to changes in the first compositereceive signal.
 14. The system of claim 12, further comprising: a firstdigital-to-analog converter (DAC) that converts the first digitalinterference cancellation signal to a first digitally-sourced basebandcancellation signal; and a first frequency upconverter that converts thefirst digitally-sourced baseband cancellation signal to a firstdigitally-sourced RF cancellation signal; wherein the first receivecoupler combines the first digitally-sourced RF cancellation signal withthe receive signal to produce the first composite receive signal. 15.The system of claim 8, wherein the first interference canceller is afirst analog canceller, and wherein the second interference canceller isa second analog canceller.
 16. The system of claim 15, wherein each ofthe first and second analog cancellers comprise a signal divider, a setof scalers and delayers, and a signal combiner.
 17. The system of claim15, wherein the first interference cancellation signal has a centerfrequency that is substantially identical to the center frequency of thetransmit signal, and the second interference cancellation signal has acenter frequency that is substantially identical to the center frequencyof the receive signal.
 18. The system of claim 8, wherein the firstinterference canceller comprises an analog canceller, and wherein thesecond interference canceller comprises a digital canceller.
 19. Thesystem of claim 18, the digital canceller further comprising: afrequency downconverter that converts the cleaned transmit signal to abaseband cleaned transmit signal; a first analog-to-digital converter(ADC) that converts the baseband cleaned transmit signal to a digitalcleaned transmit signal; a signal component generation system, coupledto the digital cleaned transmit signal, that generates a set of signalcomponents from the cleaned transmit signal; a multi-rate adaptivefilter that transforms the set of signal components into a digitalinterference cancellation signal according to a transform configuration;a digital-to-analog converter (DAC) that converts the digitalinterference cancellation signal to the second interference cancellationsignal.
 20. The system of claim 19, wherein the second receive couplercombines the second interference cancellation signal and the firstcomposite receive signal to produce a second composite receive signal,and further comprising a transform adaptor that dynamically sets thetransform configuration of the digital canceller in response to changesin the second composite receive signal.
 21. The system of claim 8,wherein the sampling interference filtering system comprises a tunablebandpass filter.
 22. The system of claim 21, wherein the tunablebandpass filter is tunable in both peak frequency response and qualityfactor.